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A thin plastic rod of length 2.6 m is rubbed all over with wool, and acquires a charge of 98 nC, distributed uniformly over its surface. Calculate the magnitude of the electric field due to the rod at a location 13 cm from the midpoint of the rod. Do the calculation two ways, first using the exact formula for a rod of any length, and second using the approximate formula for a long rod.

Respuesta :

Answer:

By exact formula

5076.59N/C

And by approximation formula

5218.93N/C

Explanation:

We are given that

Length of rod,L=2.6 m

Charge,q=98nC=[tex]98\times 10^{-9} C[/tex]

[tex]1nC=10^{-9} C[/tex]

a=13 cm=0.13 m

1 m=100 cm

By exact formula

The magnitude of  the electric field due to the rod at a location 13 cm from the midpoint of the rod=[tex]\frac{kq}{a}\times \frac{1}{\sqrt{a^2+\frac{L^2}{4}}}[/tex]

Where k=[tex]9\times 10^9[/tex]

Using the formula

The magnitude of  the electric field due to the rod at a location 13 cm from the midpoint of the rod=[tex]\frac{9\times 10^9\times 98\times 10^{-9}}{0.13}\times \frac{1}{\sqrt{(0.13)^2+\frac{(2.6)^2}{4}}}=5076.59N/C[/tex]

In approximation formula

a<<L

[tex]a^2+(\frac{L}{2})^2=\frac{L^2}{4}[/tex]

Therefore,the magnitude of  the electric field due to the rod at a location 13 cm from the midpoint of the rod=[tex]\frac{kq}{a}\times \frac{1}{\sqrt{\frac{L^2}{4}}}[/tex]

The magnitude of  the electric field due to the rod at a location 13 cm from the midpoint of the rod=[tex]\frac{9\times 10^9\times 98\times 10^{-9}}{0.13}\times \frac{1}{\sqrt{\frac{(2.6)^2}{4}}}=5218.93N/C[/tex]